swq 04 guidance

8/6/2019 SWQ 04 Guidance

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August 15, 2003

Guidance for AssessingTexas Surface and Finished Drinking

Water Quality Data, 2004

Texas Commission on Environmental Quality

Office of Compliance and Enforcement

Monitoring Operations DivisionSurface Water Quality Monitoring Program


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For information about this guidance, contact the:

Texas Commission on Environmental Quality

Surface Water Quality Monitoring Program

MC-150P.O. Box 13087

Austin, Texas 78711-3087

Fax: (512) 239-4420

or E-mail:

[email protected]

This guidance is also available on the TCEQ Web site,

www.tnrcc.state.tx.us/water/quality/305_303.html.

Or, from the home page, use the Site Search to look for Water Quality Inventory 2004.


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Table of Contents

General Assessment Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Waters Covered in Assessments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Sources of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Period of Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Frequency and Duration of Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Minimum Number of Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Use of the Binomial Method for Establishing Required Number of

Exceedances for Partial and Nonsupport of Designated Uses . . . . . . . . . . . 6

Flow Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Values Below Limits of Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Spatial Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Depth of Water Quality Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Determination of the Mixed Surface Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Determination of Tidal Influence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Methodology for Assessing Use Support and Primary Concerns . . . . . . . . . . . . . . . . 19

Aquatic Life Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Dissolved Oxygen Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Toxic Substances in Water Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Ambient Water and Sediment Toxicity Tests . . . . . . . . . . . . . . . . . . . . . . . 33

Biological and Habitat Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Fish Community Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Benthic Macroinvertebrate Community Assessment . . . . . . . . . . . . 36

Aquatic Life Use Support Determination

Using Bioassessment Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Determination of Criteria Support for Protectionof Aquatic Habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Contact Recreation Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Noncontact Recreation Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Public Water Supply Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Finished Drinking Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Fish Consumption Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Oyster Waters Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Approved Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Conditionally Approved Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Restricted Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Prohibited Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Threatened Water Bodies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Methodology for Assessing General Uses and Primary Concerns . . . . . . . . . . . . . . . 51

Methodology for Assessing Secondary Concerns . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Nutrients and Chlorophyll a Screening Levels . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Sediment Quality Screening Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Fish Tissue Screening Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Public Water Supply Concerns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59


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Narrative Concerns and Nonsupport of Narrative Criteria . . . . . . . . . . . . . . . . . 60

Monitoring Strategy to Strengthen Assessments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Methodology for Assignment of Causes and Sources of Pollutants . . . . . . . . . . . . . . 74

AppendixesAppendix A. Sample Sizes and Number of Exceedances Required to

Determine Partial Support of a Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Appendix B. Sample Sizes and Number of Exceedances Required to

Determine Nonsupport of a Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

Appendix C. Samples Sizes and Number of Exceedances Required to Determine Primary

Concerns and Partial Support of the Aquatic Life Use . . . . . . . . . . . . . . . . . . . 85

Appendix D. Sample Size and Number of Exceedances Required to Determine

Secondary Concerns (or Primary Concerns for Bacterial Indicators) and

Nonsupport of Aquatic Life Use Acute Criteria . . . . . . . . . . . . . . . . . . . . . . . . 86

List of Tables

Table 1. Summary of Type I and Type II Error Rates Associated with Using Simple

Percentage Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Table 2. Sample Sizes and Number of Exceedances Required to Determine

Partial Support of a Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 3. Sample Size and Number of Exceedances Required to Determine

Nonsupport of a Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Table 4. Sample Size and Number of Exceedances Required to Determine Primary Concerns

and Partial Support of Aquatic Life Use Acute Criteria . . . . . . . . . . . . . . . . . . . . . . 11Table 5. Sample Size and Number of Exceedances Required to Determine

Secondary Concerns (or Primary Concerns for Bacterial Indicators)

and Nonsupport of Aquatic Life Use Acute Criteria . . . . . . . . . . . . . . . . . . . . . . . . 12

Table 6. Framework for Evaluating Use Support and Primary Concerns . . . . . . . . . . . . . . . 20

Table 7. Criteria for Specific Metals in Water for Protection of Aquatic Life . . . . . . . . . . . . 30

Table 8. Criteria in Water for Specific Organic Substances for Protection of

Aquatic Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table 9. Index of Biotic Integrity Scoring and Evaluation

Statewide Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Table 10. Metrics and Scoring Criteria for Surber Samples -

Benthic Macroinvertebrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Table 11. Metrics and Scoring Criteria for Kick Samples, Rapid BioassessmentProtocol - Benthic Macroinvertebrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Table 12. Habitat Quality Index Scoring and Evaluation Criteria . . . . . . . . . . . . . . . . . . . . . . 40

Table 13. Decision Matrix for Integrated Assessments of Aquatic Life Use (ALU) Support

Based on Bioassessment, Dissolved Oxygen, Toxics in Water,

and Toxicity in Water Testing Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41


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Table 14. Maximum Contaminant Levels for Organic Chemicals in

Public Drinking Water Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Table 15. Maximum Contaminant Levels for Inorganic Chemicals in

Public Drinking Water Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Table 16. Human Health Criteria in Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Table 17. Framework for Evaluating General Use Support . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Table 18. Framework for Identifying Secondary Concerns . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Table 19. Screening Levels for Metals in Sediment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Table 20. Screening Levels for Organic Substances in Sediment . . . . . . . . . . . . . . . . . . . . . . 62

Table 21. Screening Levels for Metals in Tissue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Table 22. Screening Levels for Organic Substances in Tissue . . . . . . . . . . . . . . . . . . . . . . . . . 69

Table 23. Targeted and Surveillance Monitoring Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Table 24. List of Causes/Stressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Table 25. List of Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Highlights

Determination of Appropriate Criteria for Unclassified Waters . . . . . . . . . . . . . . . . . . . . . . . . . 13


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Guidance for Assessing TexasSurface and Finished DrinkingWater Quality Data, 2004

General Assessment MethodologyThe Texas Commission on Environmental Quality (TCEQ) administers

water quality management programs with the goal of protecting, maintain-

ing, and restoring Texas water resources. The Texas Surface Water

Quality Standards (TSWQS, TCEQ Rules Chapter 307), adopted by the

TCEQ on July 26, 2000, although not yet approved by the Environmental

Protection Agency (EPA), recognize the regional and geologic diversity of

the state by dividing major river basins, bays, and estuaries into defined

segments (referred to as classified segments). Appropriate water uses

such as aquatic life, contact recreation, or oyster watersare designated

for each of the classified segments. Numerical criteria (concentrations)established in the TSWQS provide a quantitative basis for evaluating use

support and for managing point and nonpoint loadings in Texas surface

waters. These criteria are used as maximum or minimum instream concen-

trations that may result from permitted discharges and nonpoint sources.

The procedure for comparing instream water quality conditions to numeri-

cal criteria is specified in the TSWQS. For example, dissolved oxygen

measurements monitored in a water body may be compared to numerical

criteria to determine if the designated aquatic life use is supported. The

TSWQS most recently adopted by the TCEQ and approved by the EPA

will be used for the assessment. The TSWQS adopted by the TCEQ on

July 26, 2000, and pending approval by the EPA, are used in this draft ofthe guidance.

Texas Drinking Water Standards (TDWS), adopted by the TCEQ on June

4, 1977 (Texas Administrative Code, Chapter 30, Sections 290.101- 121),

and revised in September 2000, ensure the safety of public water supplies.

Numerical criteria established in the TDWS forfinished water(after

treatment) provide a quantitative basis for evaluating support of the public

water supply use.

In most instances, this guidance describes how numerical criteria can be

compared to conditions within streams and rivers, lakes and reservoirs,and ocean waters, as specified in the TSWQS/TDWS. For example,

dissolved oxygen criteria consist of 24-hour average and absolute mini-

mum concentrations. Monitoring must be conducted over at least one

complete 24-hour period to generate dissolved oxygen data that can be

directly compared to the criteria. Automatic equipment is typically used at

monitoring sites to collect field measurements over a complete 24-hour

period. In some cases, instantaneous measurements made at equally-


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spaced intervals over a 24-hour period are used to generate the required

data for direct comparison to the dissolved oxygen criteria.

Some of the numerical criteria in the TSWQS, such as water temperature,

pH, chloride, sulfate, and total dissolved solids, are not associated with

single, specific uses. Instead, they were established in the TSWQS to

ensure support of multiple uses, and as tools to identify and manage the

influences of point and nonpoint sources of pollution (see definitions on

page 73).

Instream concentrations of nutrients and chlorophyll a, toxic substances in

sediment, and toxic substances in fish tissue are useful in identifying water

quality concerns and in evaluating the causes of nonsupport of the narra-

tive standards. Numerical criteria for these constituents have not been

established in the TSWQS. The screening levels (instream concentrations)

for these parameters establish targets that can be directly compared to

monitoring data. The screening levels are statistically derived from long-

term monitoring data for this guidance. Recent monitoring data, collected

over the last five-year period, are compared to the screening levels to

identify areas where elevated concentrations are causes of concern.

The TSWQS also contain narrative criteria (verbal descriptions) that apply

to all waters of the state. Narrative criteria include general descriptions,

such as existence of excessive aquatic plant growths, foaming of surface

waters, taste- and odor-producing substances, eroding sediment, and toxic

materials. Narrative criteria are evaluated by using numeric criteria, if they

are available. Other informationincluding water quality studies, exis-

tence of fish kills or contaminant spills, photographic evidence, local

knowledge, and best professional judgmentis also used to identify

narrative criteria concerns and evaluate support of narrative criteria and

associated designated uses.

To conduct the assessment, the most recent five years of surface water

quality monitoring and finished drinking water data are assembled,

ordered by parameter, and evaluated by analysts. In most cases, individual

values for each parameter are compared to either numerical water quality

criteria or screening levels, and the number of exceedances are deter-

mined. Uses and criteria are assessed asfully supported,partially sup-

ported, and ornot supportedbased on the number of exceedances for agiven sample size. Similar exceedances of numeric screening levels are

used to identify water bodies with no concerns, orconcerns for impair-

ment. In a few cases where numeric criteria are established as averages

(dissolved oxygen criteria; chloride, sulfate, and total dissolved solids

criteria; chronic criteria for toxic substances; public drinking water

criteria; and human health criteria), individual concentrations for each

parameter are summed, and an average is computed. The average is then

directly compared to criteria in the TSWQS/ TDWS to determine if the


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designated use is fully supported or not supported, or to identify water

quality concerns.

Waters Covered in Assessments

All stream, reservoir, estuary, and Gulf of Mexico sites are evaluated if

there is sufficient water quality data to assess at least one designatedbeneficial use or criterion. This includes sites within classified segments,

as specified in the TSWQS, and sites off classified segments (unclassified

waters). The general criteria in the TSWQS for the following uses should

be applied to assessment of classified and unclassified waters, unless site-

specific criteria derived from receiving water assessments are available:

C aquatic life use (dissolved oxygen, toxic substances in water, water

and sediment toxicity tests, and biological assessments),

C contact recreation use, and

C fish consumption use (human health criteria, fish consumption

advisories, and aquatic life closures).

Narrative criteria should be applied to assessment of unclassified waters

unless site-specific criteria derived from receiving water assessments are

available. Site-specific criteria developed for classified segments (water

temperature, pH, chloride, sulfate, and total dissolved solids) do not apply

to unclassified water bodies.

Sources of Data

Information that may be considered includes surface water quality moni-

toring (SWQM) data stored in the TCEQ Regulatory Activities and

Compliance System (TRACS) database, finished drinking water quality

data in the TCEQs Water Permits and Resource Management databases,

Clean Rivers Program (CRP) databases, volunteer monitoring programs,

and/or other quality-assured data. Water quality data used in the assess-

ment must meet clearly defined acceptance and time line criteria estab-

lished by the TCEQ (refer to most recent revision ofMethodology for

Developing the Texas List of Impaired Water Bodies).

In addition to SWQM data collected by the TCEQ, the TRACS database

contains quality-assured data from other state and federal agencies, river

authorities, cities, and other monitoring groups. State agencies include theTexas Department of Health (TDH) and the Texas Parks and Wildlife

Department (TPWD). Federal agencies include the U.S. Geological

Survey (USGS) and the International Boundary and Water Commission

(IBWC). These data are collected using methods consistent with the

Surface Water Quality Monitoring Procedures Manual(TCEQ, GI-252).

SWQM data are collected at fixed stations during routine monitoring and

from many other sites selected for special studies and intensive surveys.

The TCEQ will also consider data included in reports and other informa-


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tion that may not be appropriate for inclusion in the TRACS data base.

TCEQ staff will evaluate these special study data to determine if they are

complete, representative, and of adequate quality.

Finished drinking water data stored in the TCEQs Water Permits and

Resource Management database are considered in assessment of the public

water supply use. Maximum contaminant levels (MCLs) for organic and

inorganic chemicals in systems using surface water supplies are assessed.

All data used in the assessment must have been collected under quality

assurance plans that ensure the data are of known and appropriate quality.

Individual measurements, especially exceedances of the water quality

criteria and screening levels, are reviewed by water quality analysts to

determine if samples are representative and accurate.

Although data which do not meet the full requirements for quality assur-

ance can not be used for regulatory purposes, it can be used for planning

and for identifying general water quality concerns.

Period of Record

All quality-assured SWQM and finished water data collected during the

most recent five-year period are considered for assessment. Most monitor-

ing groups collect data at fixed sites at recurring quarterly or monthly

frequencies. For most sites, approximately 20 samples or measurements

are available for assessments. In some casesparticularly for toxicants in

water, sediment, and fish tissuesamples may be collected less frequently

at fixed sites.

In some instances where water quality has dramatically improved or

declined recently, the more recent and representative data set may be used

for the assessment. These changes in water quality could be due to identi-

fied permanent changes in pollutant loadings, such as a new treatment

facility, implementation of best management practices, or hydrologic

changes. Data older than five years may be used for some assessment

purposes at the discretion of TCEQ water quality program staff. Such uses

may include the determination of trends or the identification of concerns

for sediment and tissue contamination.

One method for determining support of the fish consumption use is theissuance of consumption advisories and aquatic life closures by the TDH.

The most recent advisory or closure is used to determine support of the

use; however, sometimes these may have been issued years prior to the

five-year assessment period.


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Frequency and Duration of Sampling

The assessment must use a sample set that is spatially and temporally

representative of conditions in the water body. Sample locations in

streams and open water bodies, such as reservoirs and estuaries, should be

characteristic of the main water mass or distinct hydrologic areas.

At a minimum, samples distributed over at least two seasons (to include

interseasonal variation) and over two years (to include interyear variation)

must be utilized, with some made during an index period (March 15 -

October 15). The data set should not be biased toward unusual conditions,

such as flow, runoff, or season. Biological sampling and 24-hour dissolved

oxygen measurements, however, must be conducted during the index

period to be considered in the assessment.

One way of ensuring that a data set is temporally representative is to use

data routinely scheduled over several years, with approximately the same

intervals of time between sampling events. This routine sampling plan canresult in monthly or quarterly sample events. No more than two-thirds of

the samples should be in one of the two years, and sampling events should

represent the different seasons.

Sediment and fish tissue samples generally do not vary greatly over time

and are considered useful integrators of water quality over time and space.

Samples collected during the most recent five years as part of a one-time

special monitoring event may be used in the assessment. For example, 15

fish samples collected on the same day from a water body would meet the

minimum sample requirement, as would 15 sediment samples collected

within a hydrologically-related area of a water body.

Minimum Number of Samples

For the 2004 assessment, the TCEQ will identify water bodies with small

datasets as partially supporting or not supporting designated uses, without

regard for samples size, provided they meet the threshold number of

exceedances and are otherwise representative (data collected over at least

a two-year period). This change in assessment procedure was imple-

mented due the certainty that small data sets that already have the thresh-

old number of exceedances will demonstrate partial or nonsupport of uses

should more samples be collected to reach a total sample size of ten.

A minimum of 10 samples is required in the following cases:

C all field measurements (dissolved oxygen, pH, and temperature);

C water quality constituents (nutrients, bacteria, chlorophyll a,

dissolved solids, and ions); and

C toxicants in water, sediment, and fish tissue collected routinely in

the water body.


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Type I Error: Inappropriately classifying a water body as partially or

not supporting, when that water body is actually fully supporting.

Type II Error: Inappropriately classifying a water body as fully sup-

porting, when that water body is actually partially or not supporting.

Historically, attainment of specific and general uses has been determined

using a simple calculation of the percentage of samples that exceed the

criteria for each water body. These criteria include dissolved oxygen,

acute toxicity, bacteria, water temperature, and pH. The TCEQ based its

impairment decision on the magnitude of this percentage. For example,

the water body was found to be fully supporting the applicable use if the

calculated exceedance rate was 10 percent or less; partially supporting if

greater than 10 percent and less than or equal to 25 percent; and not

supporting if greater than 25 percent. This method does not address the

previously described probability for committing decision errors when

analyzing the behavior of random variables like those associated with

water quality.

The binomial methodis a useful tool for estimating the probability of

committing Type I and/or Type II errors for situations when the analysis is

based on a given variable that falls into one of two categories. Placing

measurements of water quality variables in two categorieseither equal

to or less than a criterion, or greater than the criterionis an example of

such a situation.

In general, when the binomial method is used, the proportion of the

population that belongs to one of the two categories (in this case the

proportion of the population that is greater than the criterion) is denoted as

p. The proportion of the population that belongs to the second category (in

this case the proportion of the population that is equal to or less than the

criterion) is denoted as q, which is equal to 1 -p. For example, for a fully

supporting water body,p is equal to or less than 10 percent (0.1), and q is

greater than or equal to 89.9 percent (0.899). In this case,p and q, respec-

tively, represent the probabilities, for a single sample event, of collecting a

sample that exceeds or a sample that meets the criterion. If one sample is

used to determine whether a water body is supporting or not, the probabil-

ity of committing a Type I error would be simple to determine in this

casethat is, 10 percent. However, the assessment of water quality datainvolves the collection of multiple samples and, in order to estimate the

probability of committing Type I and/or Type II errors, cumulative proba-

bilities must be determined.

The binomial method can be used to calculate the probability of collecting

more than 10 percent exceedances from a water body that actually con-

tains less than 10 percent (0.10) exceedancesthat is, erroneously classi-

fying a water body as partially supporting for each combination of number


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of samples (n) and number of exceedances (e). For example, the binomial

method can be used to determine the cumulative probability of collecting

two or more exceedances out of 9 samples when the actual exceedance

rate in a water body is 10 percent. This cumulative probability represents

the Type I error probability. By calculating these cumulative probabilities

for each combination of n and e, it becomes possible to select the combi-

nation which provides an acceptable probability of committing Type I

and/or Type II errors.

Based on this process of analyzing error rates using the binomial method,

the TCEQ has recognized that the chance of falsely classifying a site as

impaired (Type I Error) is relatively high for the historically utilized

method. For example, basing decisions on the simple percentage exceed-

ance calculation of 10 percent results in a 26.4 percent to 61.2 percent

chance of falsely classifying a water body as impaired (Table 1).

Table 1. Summary of Type I and Type II Error Rates Associated with UsingSimple Percentage Approach

Summary of Type I and Type II Error rates associated with using simple percentage approach to

determine partial support for sample sizes from 4 to 20.

Sample Size

(n)

Number of Exceedances

Required (e) to Classify

Water Body as Partially

Supporting

Exact Binomial

Type I Error Rate,

Assuming 10% Actual

Exceedance Rate

Exact Binomial

Type II Error Rate

Assuming 11% Actual

Exceedance Rate

20 3 32.3 40.5

19 2 58.0 39.2

18 2 55.0 39.0

17 2 51.8 37.8

16 2 48.5 38.8

15 2 45.1 38.8

14 2 41.5 38.4

13 2 37.9 38.3

12 2 34.1 38.0

11 2 30.3 37.8

10 2 26.4 37.6

9 1 61.2 35.0

8 1 56.9 34.4

7 1 52.2 33.9

6 1 46.8 34.0

5 1 40.9 32.8

4 1 34.4 31.6


15/93

August 15, 20039

For partial support and nonsupportdefined as exceedance rates of more

than 10 and 25 percent, respectivelythe number of exceedances required

for any given number of samples from 10 to 20 is presented in Tables 2

and 3. The number of exceedances was selected to maintain a Type I error

probability below 20 percent for all standards and criteria, except acute

criteria to support aquatic life, where the probability is below 50 percent.

This is reflected by the error rate range for Type I error probabilities of 6.8

to 18.4 in Table 2, and 7.8 to 18.9 in Table 3.

To determine if there are primary concerns (for parameters with numeric

water quality standards), the number of exceedances required for any

given number of samples from 4 to 20 are shown in Table 4. These criteria

were selected to maintain a Type 1 error probability below 50 percent.

For secondary concerns (for parameters where water quality standards are

not adopted), the number of exceedances required for any given number of

samples from 4 to 20 are shown in Table 5. These criteria were selected to

maintain a Type 1 error probability below 50 percent.

Table 2. Sample Sizes and Number of Exceedances Required to DeterminePartial Support of a Use

(Error rates for sample sizes greater than 20 are provided in Appendix A.)

Minimum number of exceedances chosen to maintain a less than 20% probability of falsely classifying water body

as partially supporting when actually fully supporting.

Sample Size(n)

Minimum

Number of

ExceedancesRequired (e)

Exact Binomial

Type I Error Rate

Assuming

10% ActualExceedance Rate

Exact Binomial

Type II Error

Rate Assuming


Exact Binomial

Type II Error

Rate Assuming


Exact Binomial

Type II Error

Rate Assuming


20 4 13.3 41.1 22.5 0.1

19 4 11.5 41.2 26.3 0.2

18 4 9.8 40.9 30.6 0.4

17 4 8.3 40.8 35.3 0.6

16 4 6.8 40.5 40.5 1.1

15 3 18.4 39.8 23.6 0.4

14 3 15.8 39.7 28.1 0.6

13 3 13.4 39.3 33.3 1.1

12 3 11.1 39.1 39.1 1.9

11 3 8.9 38.6 45.5 3.3

10 3 7.0 38.3 52.6 5.5


16/93

August 15, 200310

Table 3. Sample Size and Number of Exceedances Required to DetermineNonsupport of a Use

(Error rates for sample sizes greater than 20 are provided in Appendix B.)

Minimum number of exceedances chosen to give a less than 20% probability of

falsely classifying water body as not supporting when actually fully supporting.

Sample Size

(n)

MinimumNumber of

Exceedances

Required (e)

Exact Binomial Type IError Rate Assuming

25% Actual

Exceedance Rate

Exact Binomial TypeII Error Rate

Assuming 26% Actual

Exceedance Rate

20 8 10.2 41.6

19 7 17.5 41.6

18 7 13.9 41.1

17 7 10.7 40.8

16 6 18.9 40.7

15 6 14.8 40.3

14 6 11.2 40.1

13 6 8 39.5

12 5 15.8 39.1

11 5 11.5 38.7

10 5 7.8 37.7

Flow Conditions

Streams are routinely monitored under highly variable flow conditions

from extreme low flows that typically occur in late summer monthsfollowing extended dry periods, to high flows that follow seasonal storm

events. Water quality criteria and screening levels generally apply to

flowing streams as long as flow exceeds the seven-day, two-year low flow

(7Q2).Low-flow criteria (7Q2) are calculated from historical USGS

stream flow records and are available for most classified streams in

Appendix B of the TSWQS. In places where low-flow criteria are not

available, they may be approximated from a downstream gaged site, or

from one located in a nearby watershed of similar size.

Many small, unclassified streams in Texas develop intermittent stream

flow in summer months and eventually become completely dry, whileothers maintain perennial pools when flow is interrupted. The decision

matrix that follows (page 13) was developed for this guidance to explain

which dissolved oxygen, toxic substances in water, and bacteria criteria

apply under different flow conditions.


17/93


18/93

August 15, 200312

Table 5. Sample Size and Number of Exceedances Required to DetermineSecondary Concerns (or Primary Concerns for Bacterial Indicators) andNonsupport of Aquatic Life Use Acute Criteria

(Error rates for sample sizes greater than 20 are provided in Appendix D.)

Minimum number of exceedances chosen to give a less than 50% probability of

falsely classifying water body as a secondary concern when actually there is no

concern, as a primary concern for bacterial indicators, or as not supporting theacute criteria when they are actually supported.

Sample Size

(n)

Minimum

Number of

Exceedances

Required (e)

Exact Binomial Type I

Error Assuming

25% Actual

Exceedance Rate

Exact Binomial Type

II Error Assuming

26% Actual

Exceedance Rate

20 6 38.3 41.6

19 6 33.2 41.4

18 5 48.1 41.1

17 5 42.6 41.0

16 5 37 40.8

15 5 31.3 40.5

14 4 47.9 39.9

13 4 41.6 39.6

12 4 35.1 39.4

11 4 28.7 38.7

10 3 47.4 38.3

9 3 39.9 37.8

8 3 32.1 37.0

7 3 24.3 36.0

6 2 46.6 35.2

5 2 36.7 33.7

4 2 26.2 31.2

those for concern. Values computed from 50 percent of minimum analyti-

cal limits that exceed criteria or screening levels are not counted as

exceedances. However, the 50 percent value of the reporting limit for

these nondetects is used in developing screening levels and in calculatingsummary statistics (minimum, maximum, and average). TCEQ staff are

investigating the application of statistical methods for treating non-detects

as part of an overall initiative to redevelop the water monitoring database

and to store more complete metadata.


19/93

August 15, 200313

Determination of Appropriate Criteria For Unclassified Waters

(1) Is the water body listed in the Texas Surface Water Quality Standards (TSWQS)

Appendix D. Site-Specific Receiving Water Assessments? Yes, go to step 2. No,

go to step 3.

(2) Does the reach from which the samples were collected fall within the description

given in Appendix D? Yes, apply appropriate criteria according to use specified in

Appendix D. No, go to step 3.

(3) Does the TCEQ Standards Team have information which allows the aquatic life use

(ALU) to be assigned? Yes, go to step 4. No, go to step 5.

(4) Apply appropriate criteria according to the flow status specified by TCEQ Standards

Team. Document the criteria and decision-making process.

(5) Attempt to determine the flow status of the water body as intermittent, intermittent

with perennial pools, or perennial, according to definitions given in TSWQS

307.3(a)(29/30):

An intermittent stream is one which has a period of zero flow for at least one weekduring most years. Where flow records are available, a stream with a 7Q2 flow of

less than 0.1 cfs is considered intermittent.

A stream that has a period of zero flow for at least one week during most years is

considered intermittent with perennial pools when adequate pools persist that would

be expected to provide habitat for significant aquatic life use. As a rule of thumb, an

adequate pool is deeper than one meter and greater than 100 meters in length, or

where large pools cover greater than 20 percent of the streambed in a 500 meter

reach.

Aperennial stream is one which does not have a period of zero flow for at least oneweek during most years.

Can a determination be made whether the water body is intermittent, intermittent

with perennial pools, or perennial, according to definition given in TSWQS

307.3(a)(29/30)? Yes, go to step 6. No, then water body is not assessed for ALU

attainment using dissolved oxygen data. Use acute criteria only to assess toxics in

water data relative to aquatic life use. A significant effort will be made during the

assessment to determine the flow status of streams with available data. Monitoring

may be needed in the years following in order to enable a flow status determination.

(6) Provide supportive information for how determination was made:

an affidavit (completed by a local resident)

flow monitoring data

biological data

other


20/93

August 15, 200314

Is water body freshwater or influenced by tidal activity? (See Determination of

Tidal Influence section in the General Assessment Methodology.)

Determine stream order according to TSWQS 307.3(a)(56) which specifies that the

smallest unbranched tributary of a drainage basin is designated afirst order stream.

Where two first order streams join, asecond order stream is formed; and where twosecond order streams join, a third order stream is formed, etc. Stream order is

determined from USGS topographic maps with a scale of 1:24,000.

If water body is intermittent:

use acute criteria only to assess toxics in water data relative to aquatic life use.

assess dissolved oxygen data relative to aquatic life use according to TSWQS

307.4(h)(4), which specifies that intermittent streams that are not specifically

listed in Appendix A or D will maintain a 24-hour dissolved oxygen average

concentration of 2.0 mg/L and an absolute minimum concentration of 1.5 mg/L.

For intermittent streams with seasonal aquatic life uses, dissolved oxygenconcentrations commensurate with the aquatic life uses will be maintained during

the seasons in which the aquatic life uses occur.

Are biological data available which allow determination of appropriate

seasonal aquatic life uses? Yes/No

If yes, assess using criteria appropriate to that use during the season that the

use exists.

If no, assess using a 24-hour dissolved oxygen average concentration of 2.0

mg/L and an absolute minimum concentration of 1.5 mg/L until such time as

biological data become available to assess seasonal uses.

If water body is intermittent with perennial pools adequate to support significant

aquatic life:

assess toxics in water data relative to aquatic life use using acute and chronic

criteria.


307.4(h)(4), which specifies that unclassified intermittent streams with significant

aquatic life uses created by perennial pools are presumed to have a limited aquatic

life use and corresponding dissolved oxygen criteria, a 24-hour average

concentration of 3.0 mg/L, and an absolute minimum concentration of 2.0 mg/L.

If water body is intermittent with perennial pools that are sustained by wastewater

treatment plant flows, and pools are inadequate to support significant aquatic life:

assess toxics in water data relative to aquatic life use using acute and chronic

criteria.


21/93

August 15, 200315


307.4(h)(4), which specifies that unclassified intermittent streams with significant

aquatic life uses created by perennial pools are presumed to have a limited aquatic

life use and corresponding dissolved oxygen criteria, a 24-hour average

concentration of 3.0 mg/L, and an absolute minimum concentration of 2.0 mg/L.

If water body is intermittent with perennial pools that are not sustained by

wastewater treatment flows, and pools are inadequate to support significant aquatic

life:

assess toxics in water data relative to aquatic life using acute criteria.


307.4(h)(4) which specifies that intermittent streams which are not specifically

listed in Appendix A or D will maintain a 24-hour dissolved oxygen average

concentration of 2.0 mg/L and an absolute minimum concentration of 1.5 mg/L.

For intermittent streams with seasonal aquatic life uses, dissolved oxygen

concentrations commensurate with the aquatic life uses will be maintained during

the seasons in which the aquatic life uses occur.

If water body is freshwater and perennial; and

(a) flow data are available and flow is >7Q2:

use acute and chronic criteria to assess toxics in water relative to aquatic life

use.


307.4(h)(1) which specifies that perennial streams, rivers, lakes, bays, estuaries

and other appropriate perennial waters that are not specifically listed in

Appendix A or D are presumed to have a high aquatic life use and

corresponding dissolved oxygen criteria; a 24-hour average concentration of

5.0 mg/L; and an absolute minimum concentration of 3.0 mg/L, 5.5, and 4.5

mg/L, respectively, in spring. For streams located in north and east Texas [as

defined in TSWQS 307.7(b)(3)(a)(ii)] assess dissolved oxygen data relative to

aquatic life use according to Table 5 in the TSWQS .

(b) flow data are available and flow is below 7Q2:

use acute criteria only to assess toxics in water data relative to aquatic life use.

do not assess dissolved oxygen data.

(c) flow data are not available:

assess dissolved oxygen data.


22/93

August 15, 200316

If water body is tidal and perennial:

use marine acute and chronic criteria to assess toxics in water relative to aquatic

life use.

use a 24-hour average concentration of 4.0 mg/L and an absolute minimumconcentration of 3.0 mg/L to assess dissolved oxygen data relative to aquatic life

use.

If water body is freshwater, perennial, and third order or greater:

use the column B value for human health protection to assess human health

criteria relative to the fish consumption use.

If water body is freshwater, perennial, and less than third order or intermittent with

perennial pools:

use 10 times the column B value for human health protection to assess humanhealth criteria relative to the fish consumption use (see exception for spring-fed

streams with a sustainable fishery).

(7) Evaluation of contact recreation use for all unclassified water bodies:

Perennial streams:

Are flow data available? Yes/No

If yes, evaluate the contact recreation use by using only bacterial indicator data

associated with sample events when flow is equal to or greater than 0.10 cfs, or

the 7Q2, if known.

If no, contact recreation is assessed.

Intermittent streams and intermittent streams with perennial pools:

bacterial indicator criteria apply at all times.

An exception to the previous guidance on nondetects is made when

evaluating chronic toxicants (aquatic life use), human health criteria forwater (fish consumption use), and primary organic substances (public

water supply use). The criteria for these constituents are expressed as

average values. In these cases, the smaller of the following measurements

is used in calculating the average: 50 percent of the reporting limit for

nondetects or 50 percent of the chronic criterion/human health criterion.

Biological monitoring, toxicity in ambient water and sediment, and tissue

monitoring are ways of identifying water quality impairments and con-


23/93

August 15, 200317

cerns for many contaminants, such as organic substances and some metals,

that are too low in concentration to be measured in ambient water. Poten-

tial contamination of the aquatic environment by these substances is

controlled through strict wastewater effluent limits.

Spatial Coverage

Water quality data are reviewed station by station within classified and

unclassified waters to determine geographical extent of designated use

support and water quality concerns. The geographic extent is estimated,

based on review of existing data, spatial distribution of monitoring sites

having the required minimum number of samples, known sources of

pollution, influence of tributaries, land use, hydrological modifications,

and best professional judgment of TCEQ and CRP assessment personnel.

Streams are measured in miles, reservoirs are measured in acres, and

estuaries and the Gulf of Mexico are measured in square miles. For large

water bodies that have only one monitoring site, the data from that one

station are not used to generate an assessment for the entire reach or area.A single monitoring site is considered to be representative of no more than

25 miles in freshwater and tidal streams and ocean shoreline. A single

monitoring site in reservoirs and estuaries is considered representative of

25 percent of the total reservoir acres and estuary square miles, but not

more than 5,120 acres or 8 square miles. Major hydrological features, such

as the confluence of a major tributary or an instream dam, may also limit

the spatial extent of an assessment based on one station. Where possible,

the SWQM Station ID number will be reported for the assessment. The

remaining area not covered by a single site will be reported as not as-

sessed.

Depth of Water Quality Measurements

Surface measurementstypically collected at a depth of one foot from the

water surfaceare generally used for assessing the following: water

temperature, chloride, sulfate, total dissolved solids, nutrients, chlorophyll

a, fecal coliform,E. coli, and Enterococci. Samples collected by the

USGS that are compositedover depth (using equal-discharge-increment or

equal-width-increment methods) may also be utilized in an assessment. In

deep streams, reservoirs, estuaries, and the Gulf of Mexico, dissolved

oxygen and pH measurements made in profile over the entire mixed

surface layerare evaluated. For toxic substances in water, individualsurface grab samples orsurface-to-bottom composite samples are evalu-

ated. Automatic multiprobe instruments used to monitor field measure-

ments over complete 24-hour periods are generally positioned between

one foot from the water surface and one-half the depth of the mixed

surface layer.


24/93

August 15, 200318

Determination of the Mixed Surface Layer

Monitoring personnel often make vertical field measurement profiles in

deep freshwater streams that are mixed from the surface to the bottom. In

these cases, all of the dissolved oxygen measurements made in the profile

during each individual sampling event are averaged, and the average is

then compared to the criterion. Individual pH measurements made in theprofile are compared to the minimum/maximum criteria. Only one exceed-

ance is counted in cases where more than one pH measurement in the

profile does not meet the minimum/maximum criteria.

The mixed surface layer for tidally influenced water bodies is defined as

the portion of the water column from the surface to the depth at which the

specific conductance is 6,000 :mhos/cm greater than the conductance at

the surface. Dissolved oxygen and pH criteria apply to the entire mixed

water column, or only to measurements made in the mixed surface layer if

the water column is stratified.

For reservoirs, the mixed surface layer is defined as the portion of the

water column from the surface to the depth at which water temperature

decreases by greater than 0.5oC. Dissolved oxygen and pH criteria apply

to the entire mixed water column, or only to measurements made in the

mixed surface layer if the water column is stratified. In rare instances,

rapid declines with depth in dissolved oxygen or pH may occur within the

mixed surface layer defined by water temperature. Best professional

judgment may be used to determine which dissolved oxygen and/or pH

measurements are included in the mixed surface layer. The information

considered for this decision will be recorded and provided with the assess-

ment.

Determination of Tidal Influence

In most cases, the extent of tidal influence in freshwater streams that drain

to tidal streams, estuaries, or the Gulf of Mexico is determined by making

field measurements (specific conductance and salinity), collecting water

samples (TDS and chloride), and observing level recorders sequentially

upstream from the streams mouths over several complete tidal cycles. In

the absence of monitored data, the tidal limit in a freshwater stream is

approximated as the point where the 5-foot contour line (5 feet above

average sea level) on a USGS topographic map crosses the stream.A water body is considered tidally influencedwhen there is observed tidal

activity, TDS is greater than or equal to 2,000 mg/L, salinity is greater

than or equal to 2 parts per thousand, or specific conductance is greater

than or equal to 3,077 mhos/cm. Marine criteria developed in the

TSWQS apply to all tidally influenced streams (classified and unclassi-

fied), estuaries, and the Gulf of Mexico.


25/93

August 15, 200319

Methodology for AssessingUse Support and Primary Concerns

A designated beneficial use is identified as partially supported or not

supported based on the number of criteria exceedances for indicators that

are protective of the use. Criteria for these indicators must be adopted in

the TSWQS. At least 10 samples must be available at each site for assess-

ment. Water bodies with designated or presumed uses that are partially

supported or not supported are placed on the 303(d) list. The framework

for evaluating designated use support is shown in Table 6.

Primary concerns are identified for indicators, such as dissolved oxygen,

that are directly tied to support of designated uses and criteria adopted in

the TSWQS. Tier 1 primary concerns are identified for indicators where

less than 10 samples are available for assessment and some exceedances

are reported. Tier 2 primary concerns are identified for indicators that

support the designated use as determined by an adequate number of

samples (10-sample minimum), but a few reported exceedances (for

example, three exceedances in 20 samples) indicate a potential water

quality problem.

Secondary concerns are identified for indicators, such as nutrients, that are

not tied to support of a designated use with a quantitative criterion. The

narrative criteria may not be supported in some cases; see the section

Narrative Concerns and Nonsupport of Narrative Criteria. Screening

levels for these indicators have generally not been adopted as standards

(with the exception of secondary drinking water standards). Water bodies

with concerns are identified in the 305(b) report, but are not placed on the

303(d) list. The TCEQ and the CRP will target enhanced monitoring to

water bodies identified with primary concerns to provide data for full use

assessment. The framework for evaluation of concerns is shown in Table 6.

Aquatic Life Use

Support of the aquatic life use is based on assessment of dissolved oxygen

criteria, toxic substances in water criteria, ambient water and sediment

toxicity test results, and biological screening levels for habitat, macroben-

thos, and fish, provided that the minimum number of samples is available.

Each set of criteria is generally evaluated independently of the others, and

impairment of the aquatic life use results when any of the individualcriteria are not attained (see Table 13).


26/93

Table 6. Framework for Evaluating Use Support and Primary Concerns

Use/Impact Assessment Method

Minimum

Number of

Samples

Designated Uses

Fully Supporting Partially Supporting Not Sup

Overall Use

Support

Evaluation of Designated

and General Uses

All uses are fully

supported.

One or more uses are

partially supported and

remaining uses are fullysupported.

One or more

supported.

Aquatic Life

Support

Intensively Collected 24-hour

Dissolved Oxygen Measurements,

Compared to the 24-hour Average

and Minimum Criteria in the

TSWQS

10 sets 10% or less of the time, the

24-hour average or

minimum concentrations

are less than the criteria

(see Table 2 for number of

exceedances required for a

given sample size).

Greater than 10% to 25%

of the time, the 24-hour

average or minimum

concentrations are less than

the criteria (see Table 2 for

number of exceedances

required for a given sample

size).

Greater than

time, the 24-h

or minimum c

are less than t

(see Table 3 f

exceedances

given sample

4-9 sets Aquatic life use not

assessed for small sample

sizes.

Aquatic life use not


sizes.

Aquatic life u

assessed for s

sizes.

Routinely Collected Instantaneous

Dissolved Oxygen Measurements

(Grabs) Compared to Absolute

Minima in the TSWQS

10 10% or less of the time,


minimum criterion (see

Table 2 for number of


given sample size).


of the time, concentrations

are less than minimum

criterion (see Table 2 for



size).

Greater than

time, concent

less than min

criterion (see

number of ex

required for a

size).

20


27/93

Table 6. Framework for Evaluating Use Support, continued


Minimum

Number of

Samples Fully Supporting Partially Supporting Not Sup

Aquatic Life

Support

(continued)



(Grabs) Compared to Absolute

Minima in the TSWQS (continued)

4-9 Aquatic life use support is

not assessed for small

sample sizes.

Aquatic life use support is


sample sizes.

Aquatic life u

not assessed f

sample sizes.



(grabs) Compared to the 24-Hour

Criteria in the TSWQS

10 Aquatic life use is not

assessed by comparing

grab samples to the 24-hour

criteria.

Aquatic life use is not

assessed by comparing

grab samples to the 24-hour

criteria.

Aquatic life u

assessed by c

grab samples

criteria.

Acute and Chronic Exposure to

Metals and Organic Substances

in Water

10 10% or less of the time, for

any individual parameter,


the acute criterion (see



given sample size)

and/or

the average is less than or

equal to the chronic

criterion.


of the time, for any

individual parameter,

concentrations exceed the

acute criterion (see Table 4

for number of exceedances


size)

Greater than

time, for any

parameter, co

exceed the ac

(see Table 5 f

exceedances

given sample

an

the average is

the chronic cr

4-9 Aquatic life use not as-

sessed for small sample

sizes.



sizes.

Aquatic life u

assessed for s

sizes.

21


28/93



Minimum

Number of


Aquatic Life

Support

(continued)

Acute or Chronic Ambient Water

and Sediment Tests

10 10% or less of the time,

conditions indicate acute

or chronic toxicity (see



given sample size).


of the time, conditions

indicate acute or chronic

toxicity (see Table 2 for



size).

Greater than

time, conditio

acute or chron

(see Table 3 f

exceedances

given sample

4-9 Aquatic life use not


sizes.



sizes.

Aquatic life u

assessed for s

sizes.

Habitat Assessment 2 See Table 13. See Table 13. See Table 13

1 Aquatic life use notassessed for one sample.

Aquatic life use notassessed for one sample.

Aquatic life uassessed for o

Biological Assessment 2 See Table 13. See Table 13. See Table 13

1 Aquatic life use not

assessed for one sample.


assessed for one sample.

Aquatic life u

assessed for o

Contact

Recreation

Bacteria Type Geo Avg Single

fecal coliform 200 400

E. coli 126 394

Enterococci 35 89

10 The long-term geometric

average is less than the

criterion

and

25% of the time or less,

concentrations are greaterthan the single sample




size).

Partial support is not

assessed.

The long-term

average exce

criterion

an

greater than 2

time, concentgreater than t

sample criter

3) for number

exceedances

given sample

22


29/93



Minimum

Number of


Contact

Recreation

(continued)



E. coli 126 394

Enterococci 35 89

4-9 Contact recreation use not


sizes.

Contact recreation use not


sizes.

Contact recre

assessed for s

sizes.

Noncontact

Recreation



E. coli 126 394

Enterococci 35 89



criterion

and


concentrations are greaterthan the single sample




size).


assessed.

The long-term

average exce

criterion

an

greater than 2

time, concentgreater than t

sample criter

3 for number

exceedances

given sample

4-9 Noncontact recreation use


sample sizes.

Noncontact recreation use


sample sizes.

Noncontact re

not assessed f

sample sizes.

23


30/93



Minimum

Number of


Noncontact

Recreation

(continued)

For Segment 2308 only


fecal coliform 2,000 4,000

E. coli 605



criterion

and


concentrations are greater

than the single sample




size).


assessed.

The long-term

average exce

criterion

an

greater than 2

time, concent

greater than t

sample criter

Table 3 for nu

exceedances

given sample

4-9 Noncontact recreation use


sample sizes.

Noncontact recreation use


sample sizes.

Noncontact re

not assessed f

sample sizes.

Public Water

Supply

Finished Drinking Water:

Organic and Inorganic MCLs

4 Running annual average is

less than the MCL.


assessed.

Running annu

exceeds the M

4 Full use support is not

assessed for this indicator

based on individual

concentrations.


assessed for this indicator

based on individual

concentrations.

Nonsupport i

for this indica

individual con

Surface Water:


10 Long-term or running

annual average of at least

four quarterly samples is

less than or equal to the

MCL.


assessed.

Long-term or

annual averag

four quarterly

exceeds the M

24


31/93



Minimum

Number of


Public Water

Supply

(continued)

Surface Water:


4-9 The public water supply

use is not assessed for

small sample sizes (unless

a running annual average

can be determined).


assessed.

The public w

use is not ass

small sample

a running ann

can be determ

Fish

Consumption

Consumption Advisories/

Aquatic Life Closures

----- No fish/shellfish

consumption

advisories or aquatic life

closures in effect.

Restricted-consumption

advisory (limits on number

or size of meals) in effect

for the general population

or a subpopulation that

could be at greater risk

(e.g., pregnant women,

children).

Aquatic life c

taking of aqu

effect

o

fish/shellfish

consumption

effect for one

species for th

population or

subpopulation

at greater risk

Human Health Criteria in Water

for Water and Fish, Freshwater Fish

Only, and Tidal-Water Fish Only

(Toxic Substances)

10 Average is less than or

equal to human health

criteria.


assessed.

Average exce

health criteria

4-9 The fish consumption use

is not assessed for small

sample sizes.


assessed.

The fish cons

is not assesse

sample sizes.

25


32/93



Minimum

Number of


Oyster

Waters

Most recent TDH Shellfish Maps,

Sanitary Surveys, and Water

Quality Data

----- Water quality data indicate

good conditions and low

densities of fecal coliformbacteria. Area approved for

growing and harvesting

shellfish.


assessed.

Area is restric

growing and

shellfish or prto water quali

based on rece

quality survey

high densities

coliform bact

All Uses Statistical Trend 20-60 over

5-20 years

Full use support is not

assessed for this indicator.

Partial use support is not

assessed for this indicator.

Nonsupport i

for this indica


33/93

August 15, 200327

Dissolved Oxygen Criteria

Each classified water body in the TSWQS is assigned one of the following

aquatic life uses, based on physical, chemical, and biological characteris-

tics: exceptional, high, intermediate, limited, orno significant aquatic life

use. Dissolved oxygen criteria (24-hour averages) to protect these aquatic

life uses for freshwater are 6.0, 5.0, 4.0, 3.0, and 2.0 mg/L, respectively. A

minimal use and dissolved oxygen screening level of 2 mg/L is used in

this guidance where the TSWQS designate no significant aquatic life use.

The dissolved oxygen criteria are 1 mg/L lower for exceptional, high, and

intermediate aquatic life uses in tidally-influenced water bodies, due to

differences between oxygen solubility in fresh and salt water.

In addition, absolute minimum criteria to protect the range of aquatic life

uses are designated. In freshwater, these minimum criteria are 4.0, 3.0,

3.0, 2.0, and 1.5 mg/L, respectively. Absolute minima in tidal waters are

nearly the same, except the criterion for the intermediate use is 2.0 mg/L,

and there is no limited use or criterion.

Unclassified perennial water bodies are presumed to have a high aquatic

life use and corresponding dissolved oxygen criteria. Unclassified inter-

mittent streams with significant aquatic life use created by perennial pools

are presumed to have limited aquatic life uses (protected by a 3.0 mg/L

criterion). Intermittent streams without perennial pools are presumed to

have minimal aquatic life uses (protected by a 2.0 mg/L criterion) when

water is flowing and exceeds the 7Q2. Presumed aquatic life uses for

unclassified streams may be changed by the results of receiving water

assessments.

A decision matrix that describes the appropriate dissolved oxygen criteria

for different flow conditions is shown on page 13. An exception to this

general rule is where site-specific aquatic life use and associated dissolved

oxygen criteria have been assigned to a perennial unclassified water body

through a receiving water assessment (see Appendix D of the TSWQS).

Another exception is for perennial streams located in the eastern and

southern areas of the state [described in the TSWQS, 307.7(b) (3)(a)(iii)]

where a strong dependent relationship exists among summertime dis-

solved oxygen concentration, stream flow, and channel bed slope. Streams

with significant aquatic life uses in these areas of the state may be evalu-

ated for 24-hour dissolved oxygen concentrations when flow is greaterthan the 7Q2, as shown in Table 1 of theProcedures to Implement the

Texas Surface Water Quality Standards (Implementation Procedures, RG-

194), adopted by the TCEQ on November 15, 2000. The headwater flows,

shown in Table 2 of the Implementation Procedures, may be used to

evaluate summertime dissolved oxygen criteria (see Table 1 of the Imple-

mentation Procedures) for presumed, designated, or assigned aquatic life

uses.


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August 15, 200328

Most of the dissolved oxygen data collected at fixed monitoring stations

are instantaneous (grab sample) measurements collected during daylight

hours (0900 to 1400 hours). Tier 2 aquatic life primary concerns are

identified by comparing instantaneous dissolved oxygen measurements to

24-hour criteria (see Table 8). Water bodies identified with Tier 2 aquatic

life primary concerns are candidates for 24-hour sampling. The water

body will be placed on the 303(d) list if impairment of the aquatic life use

is indicated by sufficient 24-hour dissolved oxygen data.

Beginning in September 1997, the TCEQ and the CRP began intensive 24-

hour monitoring of dissolved oxygen and other field measurements at

many sites. This type of monitoring is targeted to water bodies where low

instantaneous dissolved oxygen levels indicate partial or nonsupport of

designated aquatic life uses. Intensive 24-hour monitoring is conducted

with automated equipment that is preset to record and store field measure-

ments at 30-minute intervals (or in some cases more frequently) over one

24-hour period. Four or more dissolved oxygen measurements may also be

made manually at even intervals over one 24-hour period at a site, as long

as one is made near sunrise (0500-0900 hours) to approximate the daily

minimum. Dissolved oxygen values recorded over the 24-hour period are

summed and divided by the number of measurements to determine the

average concentration, which is compared to the 24-hour criterion. The

lowest dissolved oxygen value from each 24-hour set is compared to the

minimum criterion.

All intensive 24-hour dissolved oxygen monitoring events must be spaced

over an index period representing warm-weather seasons of the year

(March 15-October 15), with between one-half to two-thirds of the mea-

surements occurring during the critical period (July 1-September 30). The

critical periodof the year is when minimum stream flows, maximum

water temperatures, and minimum dissolved oxygen concentrations

typically occur in Texas streams. A period of about one month must

separate each 24-hour sampling event. When samples are available from

outside the index period, these samples can be used to indicate nonsupport

of the criterion at the discretion of TCEQ staff.

For purposes of determining compliance with 24-hour average criteria,

samples collected near the surface will be considered representative of the

mixed surface layer. In deep streams, reservoirs, and tidally-influencedwater bodies, automatic equipment may be positioned at one-half the

depth of the mixed surface layer for compliance purposes. At least ten 24-

hour monitoring events (using 24-hour criteria and/or absolute minimum

criteria) at each site within a five-year period are required to provide

adequate data for assessment of the aquatic life use (Table 6). A Tier 1

primary concern is identified if only 4 to 9 samples are available. A Tier 2

primary concern is identified when there are 10 or more samples and the

evidence is compelling (2 or more samples exceed rating criteria).


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August 15, 200329

Toxic Substances in Water Criteria

Support of the aquatic life use, based on toxic chemicals in water, includes

an evaluation of those metals and organic substances for which criteria

have been developed. The TCEQ has developed water quality criteria in

the TSWQS for 12 metals and 26 organic substances (see Tables 7 and 8).

Acute criteria apply to all waters of the state except in small zones of

initial dilution near wastewater discharge points. Chronic criteria apply

wherever there are aquatic life uses outside of mixing zones in intermittent

streams that maintain large perennial pools, and in flowing streams when

the stream flow is greater than the 7Q2. Refer to the decision matrix on

page 13 for a more detailed explanation of which toxic substances in water

criteria apply at different flow conditions.

For evaluation of acute toxicity, individual measurements of 12 metals

and 26 organic substances are compared against acute criteria established

in the TSWQS (Table 1 in the TSWQS). Selection of which set of criteria

(freshwater or tidal water) to use in the comparison is based on the loca-

tion of the station; for example, for a station located in tidally influenced

water, the marine criteria are applicable. Ten or more samples are required

to evaluate support of the aquatic life use (Table 6). A Tier 1 aquatic life

primary concern is identified if only 4 to 9 samples are available. Tier 2

concerns are not identified for acute criteria.

For several toxic substance parameters where toxicity is defined as a

function of pH or hardness, acute criteria are expressed as an equation

based on this relationship. Appropriate pH and hardness values of long-

term SWQM fixed station network data by segment are used to compute

criteria (see Table 5 in the Implementation Procedures). Where segment-

specific criteria are not available, those developed for the entire basin may

be used (see Table 2 in the TSWQS). In other instances where 30 or more

ambient samples are available at a site, pH and hardness values are ranked

from the lowest to the highest, and the low 15th percentiles are used to

compute criteria for a specific site or the entire water body. If hardness

values are available for the day at the site that the toxicant was collected,

criteria calculated for that day can be applied to the sample.

The TSWQS express the criterion forsilverin thefree ionic form. Silver

data in the SWQM database are reported as the dissolved fraction. The

percentage of dissolved silver that is present in the free ionic form iscalculated and compared to the criterion. Silver data collected from a

variety of water bodies throughout the United States indicate that a corre-

lation exists between the dissolved chloride concentration and the percent

free ionic silver.


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Table 7. Criteria for Specific Metals in Water for Protection of Aquatic Life

(All values listed or calculated in :g/L. Hardness concentrations are input as mg/L)

Parameter Code Parameter Freshwater Acute Freshwater Chronic

T

01106 Aluminum (d) 991w 01000 Arsenic (d) 360w 190w

01025 Cadmium (d) 0.973wQ(1.128(ln(hardness))-1.6774)

0.909 wQ(0.7852(ln(hardness))-3.490)

01030 Chromium (Tri)(d) 0.316wQ(0.8190(ln(hardness))+3.688)

0.860wQ(0.8190(ln(hardness))+1.561)

01040 Copper (d) 0.960wQ(0.9422(ln(hardness))-1.3844)

0.960wQ(0.8545(ln(hardness))-1.386)

00722 Cyanide (free) 45.8 10.7

01049 Lead (d) 0.889wQ(1.273(ln(hardness))-1.460)

0.792wQ(1.273(ln(hardness))-4.705)

71900 Mercury (t) 2.4 1.3

01065 Nickel (d) 0.998wQ(0.8460(ln(hardness))+3.3612)

0.997wQ(0.8460(ln(hardness))+1.1645)

01147 Selenium (t) 20 5

01075 Silver (d)(f) 0.8w

01090 Zinc (d) 0.978wQ(0.8473(ln(hardness))+0.8604)

0.986wQ(0.8473(ln(hardness))+0.7614)

(d) - dissolved fraction

(t) - total metal

(f) - criteria corrected to free ionic form for individual samples

w - Indicates that a criterion is multiplied by a water-effects ratio in order to incorporate the effects of local water chemistry on

1 except where sufficient data is available to establish a site-specific, water-effects ratio. Water-effects ratios for individua

the TSWQS when standards are revised. The number preceding the w in the freshwater criterion equation is an EPA conve

30


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Table 8. Criteria in Water for Specific Organic Substances for Protection of Aquatic Life

(All values listed or calculated in :g/L)

Parameter

Code Parameter Freshwater Acute Freshwater Chronic

Tidal Water

Acute

Pesticides

39330 Aldrin 3.0 --- 1.3

39350 Chlordane 2.4 0.004 0.09

81403 Chloropyrifos (Dursban) 0.083 0.041 0.011

39750 Carbaryl 2.0 613.0

39370 4,4' - DDT 1.1 0.001 0.13

39560 Demeton 0.1

39780 Dicofol (Kelthane) 59.3 19.8 ----

39380 Dieldrin 2.5 0.002 0.71

39650 Diuron 210.0 70.0

Endosulfan I (alpha) 0.22 0.056 0.034

Endosulfan II (beta) 0.22 0.056 0.034

34351 Endosulfan sulfate 0.22 0.056 0.034

39390 Endrin 0.18 0.002 0.037

39782 gamma-Hexachlorocyclohexane 2.0 0.08 0.16

39580 Guthion 0.01

39410 Heptachlor 0.52 0.004 0.053

39530 Malathion --- 0.01 ---

39480 Methoxychlor --- 0.03 ---

39755 Mirex --- 0.001 ---

39540 Parathion (ethyl) 0.065 0.013 ---

39516 PCBs, total 2.0 0.014 10

31


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Table 8. Criteria in Water for Specific Organic Substances for Protection of Aquatic Life, continued

Parameter

Code Parameter Freshwater Acute Freshwater Chronic

Marine

Acute

39032 Pentachlorophenol e[1.005(pH) - 4.830]

e[1.005(pH) - 5.290]

15.1

39400 Toxaphene 0.78 0.0002 0.21

Tributyltin (TBT) 0.13 0.024 0.24

77687 2,4,5 Trichlorophenol 136 64 259

Semivolatile Organic Substances

34461 Phenanthrene 30 30 7.7

32


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August 15, 200334

acute and 7-day chronic toxicity tests on ambient water and sediment

elutriates using Ceriodaphnia dubia (water flea) andPimephales promelas

(fathead minnow) in freshwater. For estuarine or saline waters (ambient

water salinity >2 ppt) and sediment, a standard 7-day chronic toxicity test

is conducted usingAmericamysis bahia (mysids) and Menidia beryllina

(inland silverside). The chronic embryo-larval test using Cyprinodon

variegatus (sheepshead minnow) is conducted over 9 days.

Support of the aquatic life use using ambient toxicity data when 10 or

more samples are available is based on the occurrence of toxicity in water

and/or sediment for given sample sizes (see Table 6). A Tier 1 aquatic life

primary concern is identified when only 4 to 9 samples are available. A

Tier 2 primary concern is identified when there are 10 or more samples

and the evidence is compelling (toxicity occurs in at least 2 samples).

Biological and Habitat Assessment

In the TSWQS, an exceptional, high, intermediate, or limited aquatic life

use is assigned to each classified water body, and to some unclassified

water bodies, based on physical, chemical, and biological characteristics

(see Appendixes A and D of the TSWQS). Biological characteristics that

describe each aquatic life use category are assessed, based on fish and/or

benthic macroinvertebrate data. For water bodies where aquatic life use

categories have been designated, use attainment can be assessed. Determi-

nation of attainment of biological characteristics deemed appropriate for

each aquatic life use category is based on the use of multimetric indices of

biological integrity which integrate structural and functional attributes. A

use attainability analysis should be undertaken in water bodies where the

designated aquatic life use has been based on information other than

biological and habitat sampling, and the use is not supported based on a

preliminary biological and habitat assessment.

Fish Community Assessment

Fish community data are collected according to field methods specified in

the TCEQReceiving Water Assessment Procedures Manual(GI-253).

These data are used to evaluate the integrity of the fish community based

on the index of biotic integrity (IBI) (Table 9). The IBI cannot be used to

assess fish community samples collected from reservoirs or tidal streams.

Draft regionalized IBI metrics have been proposed by the Texas Parks and

Wildlife Department (Regionalization of the Index of Biotic Integrity forTexas Streams, draft TPWD publication). Ultimately, these regionalized

IBIs are the preferred assessment tool. However, until the draft regional-

ized IBIs are finalized in 2001, data will be evaluated using statewide

criteria, and the draft regionalized IBIs will be used as a supplemental

assessment tool. For example, the regionalized IBI may be used to catego-


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Table 9. Index of Biotic Integrity Scoring and Evaluation Statewide Criteria

Category Metric 5

S

Species richness and composition 1. Total number of fish species

2. Number of darter species

3. Number of sunfish species

(excluding bass)

4. Number of sucker species

5. Number of intolerant species

6. Percentage of individuals as tolerants

*

> 3

> 2

> 2

> 3

< 5% 5

Trophic composition 7. Percentage of individuals as omnivores

8. Percentage of individuals as insectivores

9. Percentage of individuals as piscivores

< 20%

> 80%

> 5%

20

>

Fish abundance and condition 10. Number of individuals in sample

11. Percentage of individuals as hybrids

12. Percentage of individuals with disease or other anomaly

> 200

0%

< 2%

>

>

>

*First-second order streams: > 7(5), 4-6(3), < 3(1)

Third-fourth order streams: > 10(5), 5-9(3), < 4(1)

Fifth-sixth order streams: > 16(5), 8-15(3), < 7(1)

Seventh-eighth order streams: > 22(5), 11-21(3), < 10(1)

Total Score for Aquatic Life Use Sub

58 - 60 Exceptional

48 - 52 High

40 - 44 Intermediate

< 34 Limited

35


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August 15, 200336

rize samples for which the IBI score obtained using the statewide metric

set falls in between categories.

Benthic Macroinvertebrate Community Assessment

Benthic macroinvertebrate data are collected according to field protocols

specified in the TCEQReceiving Water Assessment Procedures Manual

(GI-253). If benthic macroinvertebrates are collected according to quanti-

tative protocols using a Surber sampler, the integrity of the benthic

macroinvertebrate community should be evaluated based on the benthic

index of biotic integrity (Table 10). If benthic macroinvertebrates are

collected according to rapid bioassessment(RBA)protocols (5-minute

kicknet, RBA snags), then the integrity of the benthic macroinvertebrate

community should be evaluated based on the metric set for evaluation of

benthic macroinvertebrate data (Table 11).

Aquatic Life Use Support Determination Using Bioassessment Data

When available, the determination of fish and/or benthic macroinverte-

brate integrity should be used in conjunction with physical and chemical

data to provide an integrated assessment of support of the aquatic life use

for water bodies identified in the TSWQS (Appendixes A and D). Support

for a given water body should be assessed according to the decision matrix

specified in Table 13, and should be based on both fish and benthic

macroinvertebrate samples. In certain instances, it may only be possible to

collect either fish or benthic macroinvertebrates. Proper justification

should be submitted, detailing why only one type of community was

sampled. After it has been determined that it is appropriate to use only fish

or only benthic macroinvertebrates, rows in Table 13 that are marked with

an asterisk may be used to interpret results. Determination of attainment

for bioassessment data (column 1, Table 13) is based on the average of the

total scores. Scores are derived for each of two or more bioassessment

events as described in Table 9 for fish, and in Table 10 or 11 for benthic

macroinvertebrates.

If only two bioassessment events are considered, then both should be

conducted in the same year during the index period March 15 to October

15, with only one of the two events occurring between July 1 and Septem-

ber 30. If more than two bioassessment events are considered, then the

period of study should be two or more years, with two events

swq 04 guidance

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